CO2 insertion chemistry as a probe of organosamarium allyl reactivity

CO2 reacts with (C5Me5)(2)Sm(eta(3)-CH2CHCH2), 1, in toluene at room temperature and with (C5Me5)(2)Sm(eta(3)-CH2CHCHR) (R = Me (2), Et (3)) in toluene at -78 degrees C to form [(C5Me5)(2)Sm(mu-O2CCH2CH=CHR)](2) (R = H (4), Me (5) Et (6)) in >90% yield. In THF, 4-6 exist as solvated monometallic species, (C5Me5)(2)Sm(mu(2)-O2CCH2CH=CHR)(THF). Crystallization of 4 from hexanes gives a bimetallic complex which contains an eight membered <(SmOCOSmOCO)over bar> ring. CS2 reacts with 1 to form (C5Me5)(2)Sm(eta(2)-S2CCH2CH=CH2), 7, which isomerizes to (C5Me5)(2)Sm(eta(2)-S2CCH=CHCH3), 8, in less than 48 h. COS reacts with 1 to form (C-5 Me-5)(2)Sm(eta(2)-OSCCH2CH=CH2), 9. Both 8 and 9 exist as monometallic species in THF, benzene, and toluene. Crystallization of 8 from toluene/phthalan gives a monometallic structure which contains a four-membered <(SmSCS)over bar> ring. CO2 also reacts with (C5Me5)(2)Sm(C6H5) in toluene to form [(C5Me5)(2)Sm(mu-O2CC6H5)](2), 10, which is dimeric in toluene and exists as a solvated monomer in THF. 10 can also be made by the reduction of benzoic acid by (C5Me5)(2)Sm(THF)(2) in THF. Similarly, reduction of terephthalic acid with 2 equiv of (C-5 Me-5)(2)Sm(THF)(2) produces [(C5Me5)(2)Sm(THF)](2)[mu-eta(2) eta(2)-(O2C)(2)C6H4], 11, which contains a single bridging [(O2C)(2)C6H4](2-) unit and two four-membered <(SmOCO)over bar> rings. X-ray crystal structures were obtained for 4, 8, 10, and 11.